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Are planes allowed to fly in circles, and is there a minimum legal altitude for takeoff and landing?
I live near a small, possibly private, airport. Every day there are small planes flying low over the neighborhood in circles for over half an hour.  They appear to just be flying for recreational purposes. They're also coming in and leaving low enough to be seen through the tree/wire lines and directly over houses.  I have seen the airport's grass runway, and it is quite large, so I don't see why the plane wouldn't be able to just land without circling so long.  Why would a pilot do this and is it legal?  Also, this is not a rural area, it is a highly-populated city.

Which country's laws are you asking about?  In the USA, this is perfectly legal.

Someone came along and edited this question to something different than what the OP was asking, so I have rolled it back.  The question was about the altitude for takeoff and landing (ie. "coming in and leaving") as well as the general circling, but not generally being too low for the area.  Yes, there is a statement about the area being populated, but that does not change what the question is.

“I have seen the airport's grass runway, and it is quite large...”.  This is very subjective. So much so that a non-aviation person can’t really judge this properly. An airport runway 5 times the length of a football field would still be considered quite a small runway. In some locations, it would be considered downright tiny. Even a runway 10 times the length of a football field would not be considered large. In some areas (New Mexico, Colorado), it would be unusable to almost all aircraft due to its length.

When you say circle I assume you mean more of a racetrack pattern, not an actual circle, right?  I have seen multiple planes in this sort of pattern, at the minimum AGL, often two at a time in the same pattern, when flying advertising banners over busy urban areas.  Of course they also are flying quite slow as well!

Most likely there’s a flight school at the nearby airport and they are conducting dual instruction flights over your neighborhood to practice ground reference maneuvers and possibly emergency procedures.  This is perfectly normal and safe.
In the United States, the following requirements for minimum safe altitudes are set for general aviation flight per 14 CFR §91.119:

Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
(b) Over congested areas. Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.
(c) Over other than congested areas. An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.
(d) Helicopters, powered parachutes, and weight-shift-control aircraft. If the operation is conducted without hazard to persons or property on the surface—
(1) A helicopter may be operated at less than the minimums prescribed in paragraph (b) or (c) of this section, provided each person operating the helicopter complies with any routes or altitudes specifically prescribed for helicopters by the FAA; and
(2) A powered parachute or weight-shift-control aircraft may be operated at less than the minimums prescribed in paragraph (c) of this section.

So unless these guys are dropping below 500 ft AGL, they’re not doing anything unusual.

@JohnDvorak - Paragraph C is in regards to persons and property not related to the operation of the aircraft. It is similar to rules against driving on sidewalks or through playgrounds. As far as your question about helicopters, that is covered in paragraph D. That covers all helicopters. It is not specific to nor does it exclude rescue and careflight helicopters. A maintenance helicopter can hover 3-6 feet from a high tension power line tower as long as it’s done in a manner and condition that is safe.

500 feet is very low to still allow proper care from power failure.. Especially considering power failure seldom happens out of the lbue.

I have to object to the phrase "This is perfectly normal and safe." The various regs make it clear that this is "safe enough" but clearly will never be 100% safe. The minimum height stuff is intended to give an aircraft with "issues" a good chance of clearing the area, precisely because there is greater danger to those on the ground.

While 500 feet AGL is low for cruise flight, it is perfectly normal and expected on the departure leg or final approach of an airport. I’ve seen airports whose runways are a mere few feet from their property line fences. Sometimes, there will be roads and/or houses on the other side of the fence. So, depending on the distance from the runway to the house, there is a high probability that every takeoff or landing will place the airplane less than 500 feet above the house. Raising the Crossing Height above an obstacle and noise abatement are reasons for a displaced threshold.

@Mike Brockington: If the planes here are in fact doing touch & goes, then obviously at two points in each circuit they will be at 500 ft AGL as they climb to and descend from pattern altitude.  Also, it's fairly difficult for an untrained person to accurately estimate altitude...

OP doesn't seem very familiar with aviation in general - so there's a distinct possibility OP is just seeing planes fly over, low and on final approach, instead of circling. OP might be confusing multiple Cessna's for being the same plane, or similar.

Or, at high altitude airports, circling may be needed on hot days in order to climb. Small planes departing Lake Tahoe in the summer, for example, frequently have to circle the area a few times to get enough altitude to get over the mountains.

The pilots in those planes are learning how to set up and execute a landing approach, which is a procedure in which the pilot follows a defined path through the air next to the airport with several segments in it during which the pilot has to progressively lower his or her altitude in defined steps. Then after taking off again, the pilot has to execute a pattern departure in much the same way. It is common for student pilots to go around and around the airport doing nothing but landing approaches and departures one after another for hours at a time, to build their flying skills.
Small, uncontrolled airports are popular for training operations because the small planes that use them do not get in the way of passenger jets, which would be a very significant safety issue.
Note that even the smallest Cessnas used for training purposes cost between 125 and 150 dollars an hour to operate, plus anywhere from 25 to 50 dollars an hour for the instructor. This means the pilots who spend an afternoon practicing landings and departures are not just idling about or killing time but are committed to what they are doing.
Finally, note that almost without exception, those little uncontrolled airports existed long before the suburbs that swallowed them up, so if there are safety concerns they should be directed at the developers who were allowed to hem in the airport and not the airport owner who got surrounded as the community grew.

"which means that they are not used for joyriding"... Huh? Plenty of people go for joy flights

but they don't shoot touch&go's for an hour just for the joy of it...

Sure they do. I and every pilot I know has done just that.

I think the point is that the "joyriding" aspect is tempered by the cost. Especially if one adds in the cost of an instructor. Private pilots choose to prioritize $150/hr rental costs over the cost of computer toys, tools for the garage, high-end photography gear or other expensive hobbies, but for most there's not an unlimited supply of cash to burn up just going in circles practicing in the pattern, just to kill time.

will edit with respect to the joyriding angle.

There's also quite a bit of difference between rental costs and ownership costs.  Since I've already paid for the plane, the incremental cost of flying is just gas & maintenance.  And since the plane is used (often well used), it could easily cost less than the SUVs and pickups that many people think nothing of owning - and let's not even get into the cost of RVs and power boats.

As far as regulations regarding minimum altitudes, Carlo has given you the official rules. But, the key words are “Except when necessary for takeoff or landing”.
In general, airplanes will descend below 500 feet Above Ground Level about a mile or so away from the beginning of the runway, along a straight line leading up to the runway (final approach) when landing. When taking off, airplanes will generally make their turn away from the airport between 400 and 1000 feet Above Ground Level. Both student pilots and veteran pilots will practice takeoffs and landings by doing what is called a touch and go. It is a series of takeoffs, a rectangular traffic pattern back to the final approach, and landings one after another. Once the airplane lands, it immediately takes off again without stopping.
There are also maneuvers called Go-Arounds for visual procedures and Missed Approaches for instrument procedures. In both of these, the aircraft will come in for a landing. But, it will initiate a climb away from the airport without touching down. This is to simulate a rejected landing in situations when it might be too hazardous to land. Go-Arounds and Missed Approaches must also be practiced.
There are also flying maneuvers that are practiced at about 800 feet Above Ground Level in order to hone and perfect flying skills. I will include a diagram of some basic flying techniques for takeoffs and landings below to better help you understand. Also, the Airplane Flying Handbook is a good reference filled with color pictures. Specifically check out the Ground Reference Maneuvers chapter.
Also, might I suggest going to the airport and asking for a discovery flight? It will give you a better understanding of what they are doing. Flying is a perishable skill. There are many things they could be and must practice. Try having a friendly conversation to learn what those things are.
By the way, in what city is your airport? “Highly populated” might mean something different to you than it does to someone living in a city with several million people. There are community neighborhoods in my multi-million person metropolis that have runways for the use of the neighborhood. The houses have hangars as well as garages. And, the streets are more numerous because some of them are for aircraft use only (aircraft always have the right of-way).

Interesting diagram - here in the UK we usually turn left onto crosswind at 500ft and we don't start our descent or change power settings until we're on base

@Dan -  I’ve never flown in the UK. I’ve spoken to pilots from the UK, Australia, and Germany. I’ve also done some ground training in South Africa. I think our 45° to downwind as well as our midfield crossover/flyover above TPA for a teardrop descent to downwind traffic pattern entries are fairly unique to the US as well. Flying crosswind at TPA at the DER in order to turn to join downwind seemed counterintuitive and not as safe to me. I would worry about the guy practicing Vx takeoffs and climbouts while I am entering crosswind for a landing.

@DeanF. I have to ask, where are you located? I have never heard of a place where "houses have hangars as well as garages. And, the streets are more numerous because some of them are for aircraft use only". I'd love to learn more about it.

@echo - Texas. We actually have airport communities. Some have houses. Some have condos and/or townhouses. Some even have two story hangars with living space on the second floor. Generally, they are Class E or G airspace. For the most part, they are nontowered. Though, they may have a small FBO/clubhouse on premises.

You said urban area, and that has an effect on things.
Crowding
Urban airports tend to be crowded out and eliminated.  They are a huge piece of real estate that developers lose their minds over, and so any business weakness in the airport is usually attacked by developers aiming to cover the property with condominiums.  Meanwhile governments want to turn them into recreational space - one commercial pilot, desperate to land anywhere, flew to his “old” military airbase and landed on their main runway - only to discover it had been converted to a dragstrip.  His record for fastest quarter-mile stands today.  And then we have NIMBYs, who labor to close airports despite knowing there was an airport there before they bought the house... present company excepted, of course.
The upshot is that the few remaining urban airports are pretty busy.   You have a lot of aircraft and a lot of traffic in/out especially on nice hobby-flying days, which I presume is when you’re outside too.
Altitude maximums
The other thing about city flying is there is usually a major airport nearby.  Now, airspaces are a lot like an upside-down wedding cake.  Near the large airport, airspace is controlled right down to the ground.  For the next ring, uncontrolled aircraft (e.g. those without expensive avionics needed to operate in controlled airspace) are allowed up to only 3000’ altitude, say.  Beyond that there’s another ring, say 7000’, and finally out to 10,500’. For you, this means that small aircraft traffic is squeezed into a narrow altitude band near the ground.
Runway use
You say “It’s a really big runway, why do they need to stack up?”  Because airport procedure is that only one plane gets to use the runway at a time, no matter how big it is - because stuff can go wrong.  Now they do make exceptions - the military (B-52 MITO) and extreme civil ops (the huge Oshkosh fly-in).  But generally, one plane at a time.
This combines with the busyness of urban small airports to make for a lot of planes in the wait pattern during busy times.
Touch-and-go’s
There’s a type of training flight called a “touch-and-go”.  In this case the pilot prepares for landing in all respects, stabilizes the landing, touches down properly, then punches up the power and lifts off again.  That is for the purpose of training landings and takeoffs, which are perishable skills.  This creates both a landing and a takeoff situation. They probably aren’t doing this during busy times, but during un-busy times, they will jump in and try to use the spare “landing slots” as it were.
I spend time around an Air Force logistics base.  They do touch-and-gos all day... with C-5 Galaxies.

Besides the (safety) related minimum altitudes and air control restricted zones for traffic management aspects of environmental (wildlife) protection, noise reduction and capacity/usage hours restrictions from municipals and states are also a thing to consider.
An airport might have existed before a new city district is built, it still might have to adjust to changing land use and zoning restrictions. So it might be helpful four you to contact local gouvernements/council.
Even the FAA has something on this topic, see for example here https://www.faa.gov/airports/environmental/airport_noise/
Ideally they might just move the waiting/practice zones, give different minimum altitudes, close for certain plane types or close of training flights earlier.


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In aircraft construction, what is the difference between a firewall and a bulkhead?
I'd like to know the difference between a firewall and a bulkhead.  They both separate segments of an aircraft, so how are they different as it pertains to their design and purpose in aircraft construction?

A bulkhead is any kind of structural panel separating two spaces in a fuselage.  Like a solid panel in the tail cone that has only small holes for cables to pass, or the panel that forms the end of the baggage area.  Pretty much any solid lateral partition with a structural use. On a large aircraft, any structural partitions separating parts of the cabin, like the flight deck bulkhead, or terminating the pressure hull at each end, the "pressure bulkheads".
A firewall is a firebreak.  It's a bulkhead that is fireproof to separate a "hot" area like an engine compartment from adjacent structure, so that if you have an engine fire, you'll have more time to try to land, or if at high altitude, say your prayers.  To be a firewall, the material of the bulkhead has to be flame resistant, with a much higher melting point than aluminum.
On GA airplanes, the firewall is usually stainless steel, but can be galvanized steel (antiques and homebuilts), or even special flame proof coatings on a normal bulkhead (some composite homebuilts).  On transport airplanes, a firewall will be stainless or titanium.
So in a nutshell, a bulkhead is a structural lateral panel in a fuselage.  A firewall is a "fireproof" bulkhead normally separating the engine compartment (or other flame source) from the rest of the plane.

This is correct. Ships notably have waterproof bulkheads engineered into their design. The Titanic's waterproof bulkheads were famously not tall enough to be effective in that particular disaster.

I would also like to add that firewalls are NOT fireproof but are there to slow the spread of fire and heat until something can be done with it. They can last a really long time, but they are all rated to fail after "a while"

Re read the middle paragraph carefully.

@RobertColumbia Both waterproof ones and fireproof ones, to be precise. Every 40 meters is a mandatory main fire zone, with a keel to top fire-resistant bulkhead. Major bulkheads under the main deck are generally waterproof, above it nothing is. Note how a bulkhead can be waterproof, fireproof, both, or neither.

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In turbojet engines, does the fan play a key role in the air intake to the inlet?
In turbojet engines, does the fan play a key role in the air intake to the inlet?

Welcome to the site! I don't understand your question, what do mean by key role?

In all three types of engines, compression turbines increase the air density in preparation for combustion.  Turbofan engines are the only ones in which the turbine portion has an additional blade extension in the front beyond the combustion chamber to increase thrust.

My question to you is, do you have a basic understanding of the different of the three engines and their construction and operation?  This question seems to be too obvious.  Actually, turboprop engines only have compressor blades, not fans.

Hi GdD. What i meant by key role was does it actually play a part in the intake of air to the engine. Because for a turbojet engine without a fan how can air be absorbed to the inlet. My understanding is that for an inlet to exist there has to be a fan to absorb air towards it. Am i right in thinking this way?

Hi Ryan. I do have a basic understanding about the three types of engines. But there is a loop hole in my understanding. I have a misunderstanding about the inlet. Does it consist with a fan? If not how does the inlet absorb air toward it?

In turbojet there is no fan. Very simply, turbofan means turbojet + fan in front connected to the LP shaft.

Further, nothing about a turbofan or turboprop requires the fan/prop on the front.  It absolutely can be set up in pusher mode, with the prop or fan behind the engine, and turbine exhaust being diffused into the fan input.  If anything, this is easier, because it means the prop/fan is on the same end of the engine as the second stage (low pressure)  compressor, so there's no need for that shaft to run all the way through the engine.  Thus reducing the need for concentric shafts.
So in that case, the engine core will input air the same way a turbojet does. There may be a second input for bypass air.

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Does a LSA or better license count for drone use?
I have a FAA private pilot license. Does that allow me the same flight privileges while flying a drone, as a FAA certificated drone pilot?

No, it does not. But because you are an "existing pilot", the application process is a little different:
FAA: Becoming a (Drone) Pilot

Existing Pilots – What to Expect
Eligibility:

Must hold a pilot certificate issued under 14 CFR part 61
Must have completed a flight review within the previous 24 months

Remote Pilot Certificate Requirements

Must be easily accessible by the remote pilot during all UAS operations
Valid for 2 years – certificate holders must pass either a recurrent online training course OR recurrent knowledge test every two years

Application Process:

Complete the online training course "Part 107 small Unmanned Aircraft Systems (sUAS) ALC-451" available on the FAA FAASTeam website – initial training course areas include:
a. Applicable regulations relating to small unmanned aircraft system rating privileges, limitations, and flight operation
b. Effects of weather on small unmanned aircraft performance
c. Small unmanned aircraft loading and performance
d. Emergency procedures
e. Crew resource management
f. Determining the performance of small unmanned aircraft
g. Maintenance and preflight inspection procedures

Complete FAA Form 8710-13 (FAA Airman Certificate and/or Rating Application for a remote pilot certificate)
a. Online or by paper (see instructions in previous section)

Validate applicant identity
a. Contact a FSDO, an FAA-designated pilot examiner (DPE), an airman certification representative (ACR), or an FAA-certificated flight instructor (CFI) to make an appointment.
b. Present the completed FAA Form 8710-13 along with the online course completion certificate or knowledge test report (as applicable) and proof of a current flight review.
c. The completed FAA Form 8710-13 application will be signed by the applicant after the FSDO, DPE, ACR, or CFI examines the applicant's photo identification and verifies the applicant's identity.
   - The identification presented must include a photograph of the applicant, the applicant's signature, and the applicant's actual residential address (if different from the mailing address). This information may be presented in more than one form of identification.
   - Acceptable methods of identification include, but are not limited to U.S. drivers' licenses, government identification cards, passports, and military identification cards (see AC 61-65 Certification: Pilots and Flight and Ground Instructors)
d. The FAA representative will then sign the application.

An appropriate FSDO representative, a DPE, or an ACR will issue the applicant a temporary airman certificate (a CFI is not authorized to issue a temporary certificate; they can process applications for applicants who do not want a temporary certificate).

A permanent remote pilot certificate will be sent via mail once all other FAA-internal processing is complete.

I got my add-on rating in a few hours by taking the course and reading the FAR. Since you already know most of the non-drone specific info from getting your pilots license, it should be easy for you to get your rating.

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How can I determine whether or not an airport has an ATIS?
Where can I find the ATIS code and frequency for an airport through a VFR chart? For example, in the case of Frankfort airport (in the attached image), I can see the AWOS frequency but I am unable to locate the ATIS code and frequency.

Actually, Im try to fill a VFR navigation log at am unable to find the information to be filled in the Airport and ATIS advisory section. My departure airport is FKR.

Who says it has an ATIS?

@GdD, if I look at the airport information using sky vector, I can see the ATIS frequency  (127.75) for this airport but I do not know about the ATIS code.

@yash - Just FYI. FKR does not have an official ATIS. It has an AWOS-3 at 124.325 MHz. The frequency you listed is for the nearby LAF ATIS at 125.75 MHz. You can use the LAF ATIS as a substitute in VFR flight when the FKR AWOS-3 is inoperative.

@yash - For IFR flight, you would substitute the TYQ AWOS-3 120.725 MHz for the FKR AWOS-3.

I don't think you understand what an ATIS code is. It's not something you can fill in before the flight.

Yes, its possible that I dont exactly understand this because I have never flown and filled an actual VFR flight plan.

The frequency for and class of the ATIS is on the VFR Sectional Chart right where you have indicated. It will also be listed in the US Chart Supplement under Weather Data Sources. The ATIS Code will never be listed as it is a function of the ATIS itself. And, it changes over time.
The left side of that section of your VFR Navigation Log is meant to be filled out shortly before takeoff. The right side of that section of your VFR Navigation Log is meant to be filled out shortly before arrival. It is helpful to have the information beforehand in your preflight planning in order to make a go/no-go decision. But, it’s primary purpose is to inform the pilot of current takeoff conditions at the time of departure and arrival. At a controlled airfield, you will be required to confirm you have the most current ATIS information by relaying the ATIS Code to ATC. That ATIS code is acquired either by listening to the ATIS over the ATIS frequency, over your cell phone at the phone number given in the US Chart Supplement, or electronically. The ATIS Code changes each time the information on the ATIS is updated. For a Class D, E, or G airport, in most cases, that is once every hour around the 45-55 minute mark. It can be more frequent for a more advanced, automated digital, non-automated, or human recorded ATIS at a Class B, C or large D airfield.
By the way, many air traffic controllers I have talked to have said that they must hear the ATIS Code either at the beginning, right after your tail number, or at the end, as the last piece of information of your initial transmission/radio call. But, I do not have any citations or references for this. Maybe another poster can provide one.

The convention is to add “with [code]” to the end of your initial contact, but ATC doesn’t really care where or how you say the code as long as it’s correct. If you don’t say it and then have an accident, they can lose their jobs even if the weather wasn’t a factor.

@StephenS - That’s the convention. Is there a rule for ATC? This comes from an FBO coffee counter debate. Some pilots say the weather info right after their tail number. Some say it whenever. The local controllers will always give the weather over the radio to any pilot who did not say the weather info at the end of their initial contact. They do not usually do the same for pilots who say it right after their tail number. The controllers stated that it was a rule they had to follow if they did not hear it at the end of the initial call. Bul they were flexible for hearing it at the start.

They just have to hear it. But an initial contact contains a lot of information they have to write down, and they’re human, so they sometimes miss pieces, especially if it’s not in the order they’re used to. If they aren’t 100% sure they heard it, they’re going to ask (or just tell you the weather, if no ATIS) rather than risk their jobs.

@StephenS - That was the point of the debate. My CFI taught to always say it anywhere you can. Other CFIs said to always say it after the tail number, before giving any other info. My personal SOP is to say it after the tail number because I like to do the most tedious or most forgotten/forgettable tasks first as GP. The controllers said that they had a rule to hear it last or read it back. But, they let those who said it first slide. But, is there an actual rule on where it should be placed. One can not be found in the FAR/AIM that I can find. Maybe in the controllers bible.

I always say it at the end out of habit, but I’ve never seen a rule on either side.

@DeanF. AIM 4-1-3(d) says the pilot wording is "Information Sierra received" but doesn't give any specific point in your transmission to say it. Personally, I just say "with Sierra" and that seems to be the default. On the ATC side, 7110.65 2-9-2(c) says that if a pilot doesn't confirm the ATIS "on initial contact" then the controller has to ask: "Verify you have information Charlie". But again, there's nothing specific about when a pilot has to state it.

@Pondlife - Yes, I give my initial contact as Blank ground/tower, Cessna ###XX with Alpha (or the weather/numbers). Distance, direction, heading (usually just inbound), altitude. Why I am calling. This works for me and keeps me from forgetting to give the weather info. I almost always get a positive response from ATC. Moving it to the end seems to be the preferred spot for ATC (based on conversations). Only if I move the weather info to another part of the transmission will ATC read the weather info back to me or ask me to confirm that I have the weather. Yet the debate goes on.

There is another FAA doc for controllers besides the FAR/AIM and the Pilot/Controller Glossary that I have not delved that far into, yet. Maybe another poster with ATC working experience can chime in.

According to the AIM 4-1-13:

The Chart Supplement U.S. indicates airports for which ATIS is
provided.

So that's the official FAA answer: look in the Chart Supplement. But, a good shortcut is that ATIS is usually available only at towered airports (there are some special cases mentioned in the AIM, like ATIS broadcast over a NAVAID, although it's still for a specific airport). The frequencies for towered airports are listed on the side of the VFR sectional:

So, looking at the edge of the sectional will give you a quick way to see airports where ATIS is available. That may not list 100% of the ATIS frequencies, but I suspect it's pretty close and certainly good enough for cross country planning.

I see no evidence that FKR/KFKR has an ATIS system, and I can’t recall ever seeing a non-towered airport that does. Even some towered airports don’t have ATIS.
As the sectional chart indicates, it does have AWOS. This is an automated system that reads the latest weather in a continuous loop, rather than an hourly recording or script by a human.
When you are departing or arriving at an airport with ATIS, you have to tell ATC that you have “information [code]” so they know you have the latest ATIS recording.
When departing or arriving at an airport with just ASOS/AWOS, you just listen to it and, if talking to ATC, advise them you have “the weather”. There is no code.
Note that if a tower is closed, its ATIS system will revert to ASOS/AWOS just like a non-towered field.

Ha ha. I just posted a correction to the OP at the same time that you posted this answer.

As others have pointed out, you seem to be mistaken as to what an ATIS is and the difference between an ATIS and an ASOS/AWOS.
An AWOS is an Automated Weather Observing System:

Automated Weather Observing System (AWOS) units are operated and controlled by the Federal Aviation Administration. These systems are among the oldest automated weather stations and predate ASOS. They generally report at 20-minute intervals and do not report special observations for rapidly changing weather conditions.

An ASOS is an Automated Surface Observing System:

Automated Surface Observing System (ASOS) units are automated sensor suites that are designed to serve meteorological and aviation observing needs. There are currently more than 900 ASOS sites in the United States. These systems generally report at hourly intervals, but also report special observations if weather conditions change rapidly and cross aviation operation thresholds.

The AWOS or ASOS will be connected to a system for "long line" dissemination (transmittal to the Internet or to ATC's flight data system) and will also be accessible to pilots locally (a computer-generated voice will read off the information over an air band frequency or over a telephone line).

Notice that both AWOS and and ASOS are observing systems. In contrast, ATIS stands for Automatic Terminal Information Service:

The continuous broadcast of recorded noncontrol information in selected terminal areas. Its purpose is to improve controller effectiveness and to relieve frequency congestion by automating the repetitive transmission of essential but routine information.

The ATIS is a broadcast of information relevant to operation at a towered airport. Of course it includes the current weather, which is actually derived from an AWOS or ASOS but is "backed up" by a human observer. But it also includes things like:

The instrument approach(es) and landing runway(s) in use
The departing runway(s) in use, if different from landing runway(s)
Airborne hazard advisories: MANPADS threat, laser illumination, low-level wind shear, available hazardous weather products, bird activity
Surface hazard advisories: shortened runway, runway condition codes, taxiway closures, construction work, snow removal operations
Other pertinent information: LAHSO in use, VFR frequencies or procedures, (non-)availability of pattern work or practice approaches, etc

Whenever any information contained in the ATIS changes, not just the weather, a new ATIS codeword is used to ensure pilots have the latest and greatest. If the only thing broadcast is the weather, a timestamp of when the observation was made is sufficient to identify what "the latest" is, which is why an AWOS/ASOS broadcast will not have a phonetic code for you to copy down. But with a general information service things besides the weather could change, meaning you can't rely on the weather observation timestamp.

As to Dean F.'s question about when ATC needs to hear the codeword: There is no rule about "at the beginning of the transmission" or "just after your tail number" or anything else. The only rule is that we have to hear you say you have the correct codeword, or we have to give you all the pertinent information. But there's a lot for us to write down and/or type in when you first call, especially if you aren't receiving radar services yet, so please forgive us if we ask you to confirm.


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Does the FAA maintain pilot records from before 1998?
I have held a PPL with an instrument rating since 1999, and I am desperate to continue, but I lost my logbook.
Is there any way to get records from the FAA about my total flying time?
I contacted my flight school, but they say they don't have a record of me, so they asked me to start over from 0 hours.
What can I do?

This is not necessarily a duplicate question, a different form can be used than was given in the other answer that provides a more comprehensive solution. AC_8060-68

If you took a checkride the FAA has your 8710 (form you would have filled out) which will have your flight times and can be used as proof of time.  Follow these steps to get your records.
You can search the airman database.  My father's and grandfather's records are in there from the 1970s and 1980s.  This just lists certificates though, no times.
You can also request a replacement certificate.  If you are a PPL then they will send you one.  You'll need to do this anyway to get the new plastic card.  Also, no times...just a certificate...which prove that you have at least the minimum flight time required to hold the certificate.
Good luck.

thank you for you're reply I'm thinking of travelling to us to get back my records and look for flight school to do my PPL so i can do CFI CFII do you think its much peter that i come my self  for a week

do i need student visa to look for my lost records with FAA and apply for new airman certificate  i find i good rate ticket to orlando

can i do all that if i fly to FL Daytona with regular visa in order for me to replace my lost records and get new PPL certificate  is 10 days enough to solve all this matters

At least since the 1970's (when I received my PPL), the FAA has had all pilot information stored and available on micro-fiche. I would expect the FAA has transferred, or at least be in the process of transferring the micro-fiche information to digital storage.
I would assume a request for a complete set of records includes print-outs of any remaining micro-fiche files and all digital storage in more recent years.
The FAA has a fee and specific form that needs to be filled out, the form is AC_8060-68 The fee is 2 dollars for each search of records, .10 cents per printed page and an optional $10 for Certification of the record.

thank you for you're reply I'm thinking of travelling to us to get back my records and look for flight school to do my PPL so i can do CFI CFII do you think its much peter that i come my self  for a week

can i do all that if i fly to FL Daytona with regular visa in order for me to replace my lost records and get new PPL certificate  is 10 days enough to solve all this matters

Well, right now our politicians have shut down the govt for non essential services so nothing is getting done.Typical inquires to the govt such as receiving "N" numbers for experimental aircraft take 2 months. But it can all be done via mail. I would suggest using a friends US physical mail address for all return requests. But who knows, perhaps foreign addresses are common requests too.

If you hold a PPL and an instrument rating, then those are locked in by virtue of having earned them.  Surely the FAA has records confirming that you are a pilot with an instrument rating, but they may not have your total times from 20 years ago.
If by chance they do, they do not have records of your individual flights, so the evidence of what you would be reporting is lost.  You will likely have to start over with 0 hours logged as a pilot with a PPL and instrument rating.
You may want to look into an electronic logbook service to prevent this from happening in the future.

thank you for you're reply I'm thinking of travelling to us to get back my records and look for flight school to do my PPL so i can do CFI CFII do you think its much peter that i come my self  for a week

can i do all that if i fly to FL Daytona with regular visa in order for me to replace my lost records and get new PPL certificate  is 10 days enough to solve all this matters

You already have your PPL.  No, 10 days will not be long enough to gather paperwork from a FSDO and then earn commercial, CFI, and CFII.
Since the last time you were here, there have been new laws created due to national security concerns (9/11, etc), so you would need to be approved through the alien flight student program at flightschoolcandidates.gov since you are not a us citizen or national.  Your chosen flight school should be able to guide you through this process.

you are right what i mean is 10 days to gather my lost documents and then fly back to my country and apply for visa ... regards my school they say you have to repeat every thing from scratch 0  and they ask for 70000 USD

Then I would say you should give your business to a different flight school.  A ppl and instrument is not "zero".

the problem is i have try many schools to get F1 visa  so i can practice CFI CFII MEI after words  F! is for  oversees student that also allow him to work as flight instructor and thats what I'm trying to do if u happened  to know any flight thats give F1 Visa please help me out

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
What should I do to resolve an incorrect birth date on my FAA medical certificate?
While taking my pre-solo exam, I noticed my medical has my birth date one year earlier than it actually is. I am expecting to solo tomorrow.
Would this error legally prohibit me from soloing until it is corrected?

Are you old enough to solo without the "extra" year of age?  Did you put the correct year in when you filled out the FAA MedXpress form?

Yes, I am old enough. I got my medical before the changes recently so my AME filled out the forms then. He must have put it in wrong by accident.

Related: How do you correct a mistake on a pilot license?

Related: Wrong hair color on my medical?

I read the FARs for this one, and there is a rule:
14 CFR §67.403 Applications, certificates, logbooks, reports, and records: Falsification, reproduction, or alteration; incorrect statements.
From what I gather, the rule is there to get liars in trouble.
If you didn't lie, which you clearly have no reason to because your age does not disqualify you, I don't think you have to worry about getting in trouble because it was the doctor's mistake.
However: (From 67.403)

(c) The following may serve as a basis for suspending or revoking a
medical certificate; withdrawing an Authorization or SODA; or denying
an application for a medical certificate or request for an
authorization or SODA:
(2) An incorrect entry, upon which the FAA relied, made in any
logbook, record, or report that is kept, made, or used to show
compliance with any requirement for a medical certificate or an
Authorization or SODA. [My emphasis]

Let's pull out the important words and we get this:
"An incorrect entry ... made in any ... record, or report that is kept ... or used to show compliance with any requirement for a medical certificate..."
A medical certificate is certainly kept or used to show compliance with a requirement to posses a medical certificate §61.3(c)(1)
You have discovered an incorrect entry.  Call the doctor that issued your medical as soon as you can in order to get it resolved, and do not accept a solo sign-off on this incorrectly filed document now that you have knowledge of the mistake.
To give you a straight answer based on my interpretation of the law, yes; this error would prohibit you from soloing until it can be corrected.


text:
How does Jeppesen create its US charts?
The Jeppesen and FAA IFR plates represent the same information in different ways. The FAA publishes its charts for free, but the underlying data that goes into the charts (e.g., exact coordinates of fixes, frequencies, etc) doesn't appear to be published in a structured format. The PDF files that the FAA publishes appear to be created using Bentley MicroStation, but do not seem to embed any useful metadata about what the various symbols mean.
Based on that preliminary research, I am wondering how Jeppesen creates their various charts, such as IFR approach plates? Do they simply take the FAA charts and manually create their own derived charts (which strikes me as tedious and error-prone)? Or is there some hidden repository of structured FAA data available somewhere that they use to create them?

The short answer is probably that they get it from here.And this question is very closely related.

FAA/NACO charts aren't masters, either
The master form of a FAA instrument approach procedure isn't the FAA/NACO approach plate for that procedure -- that plate is a derived document, just like the Jeppesen plate for that approach is.
The master, instead, is kept by the FAA in textual form as a set of Form 8260s. These provide a precise, formulaic description of any FAA approach procedure -- they're simply not in a form that's at all usable in the cockpit.
An example set of 8260s for the (rather special) KASE LOC/DME 15 approach can be found here.  Note that this contains exact records of fixes, governing obstacles, holds, and other procedure parts, as well as documentation about standards waivers and notes of changes.

That's quite an elaborate (and unstructured) document! Do you happen to know how it relates to the Coded Instrument Flight Procedures (CIFP) database at https://www.faa.gov/air_traffic/flight_info/aeronav/productcatalog/digitalproducts/cifp/ ?

"The National Flight Data Center (NFDC) is one element within AJV-5 with respect to maintaining the National Airspace System Resources (NASR) database and for disseminating information relating to the NAS. NFDC is also responsible for maintaining proposed data within the AIRNAV database for the development of instrument flight procedures." Source: Order 8260.19,  Flight Procedures and Airspace

@MarcPrud'hommeaux: In addition of my previous comment: "The National Airspace Systems Resources (NASR) team currently provides [...] Process all aeronautical source data published by the NASR and IFP databases for inclusion in the Coded Instrument Flight Procedures (CIFP)" Source.

Not only does Jeppesen create there documents from the same raw data that NACO uses (in the US), they provide charts, plates, and databases covering most of the world.  That requires collecting the raw data in various formats from dozens of different governments and agencies around the world and converting it all to their standard on a 28-day update cycle.

Considering that Jeppesen provides their products in several different formats, such as the paper charts, their JeppView application for iPad EFB's, and database subscriptions for aircraft Flight Management Systems, it seems highly likely that they use a database of their own -- and a massive one at that!
Beyond what is publically available, they offer a service to major subscribers (i.e. airlines) to "tailor" some or even all of the approach charts.  While they can't change the FAA's minimums in a way that makes them less restrictive, they can do other things with them.  For instance, if Sky Air only flies aircraft that are approach category C, then the tailored charts might remove the Cat A, B, and D minima.  Also, if they always use the altitude alerter in the aircraft for non-precision approaches, they might have Jeppesen round the non-precision approach minima up to the next 100' increment.
I've also seen tailored charts that address Category II and Category III approach minimums.  The generic chart might show both Cat IIIA and IIIB minima, but if the airline was only approved for IIIA operations, the tailored charts wouldn't have the IIIB info.  Or an airline that only used autoland would omit notes about using a HUD for approaches below Cat I, while an airline that only uses a HUD and not autoland could do the reverse.
When a published change from the FAA affects a point on the chart (say, a feeder fix to the ILS course itself), then every chart with that point will have to be re-issued, and that could affect dozens or even hundreds of charts -- and attempting to ensure that process works as a manual process would be nearly impossible.  A database that includes the ability for a Jeppesen charting specialist to say, "show me every chart with the point 'JEBBB' on it" would make that process a lot more reliable.
When you see some of the new products that they have in development for the iPad, such as SID and STAR charts that are to-scale and geo-referenced -- allowing the magenta aircraft symbol to "fly" along the points of the chart -- and with significant terrain screened in as a dim underlay to the graphics, it becomes clear that they are only producing these sorts of products out of a database, and not created by hand.


text:
Will the NTSB be involved in the investigation of the crash that killed the President of Iran?
On 19 May 2024, the President of Iran died following the crash of a Bell helicopter, originally built in America.
My understanding is that following the crash of an aircraft, the international aviation treaties allow the aviation regulator of the country of the aircraft's origin to join the investigation.
Have the NTSB, the broader US government, or the Iranian government made any statements regarding the involvement of the NTSB in the investigation into this crash?
I'm not asking for speculation about what might have happened or what might happen, but about the law of the air and official government statements.

Interesting question. One for which the answer is, most likely "time will tell", and will, probably get closed. This is at least as much a political question as it is aviation.

As it turns out, not only is it an interesting question, it has an interesting answer and probably will not get closed!

In short:
For a civil use of the aircraft, pursuant to Chicago Convention, the US Government, as the government of the State where the aircraft was designed/manufactured, would be entitled to designate a representative for the investigation (§4.6 of Annex 13).
But the aircraft was operated by Iran Air Force, making it a State aircraft, for which the Convention doesn't apply (Art. 3 of the Convention).
There is no international treaty which can be invoked to participate to the investigation. Iran is sovereign in how they will conduct the investigation, with whom, and whether they will share any finding or conclusion.
As far as I know, nobody has publicly released a statement or a request for a participation to the investigation.

International Civil Aviation Convention

My understanding is that following the crash of an aircraft, the international treaties governing flight allow the aviation regulator of the country of the aircraft's origin to join the crash investigation.

Iran is part of the signatories of Chicago Convention. ICAO Annex 13 to the Convention is perfectly clear about participation to an aircraft accident investigation (§4.6):

In accordance with 5.18, the State of Registry, the State of the Operator, the State of Design and the State of Manufacture have the right to appoint an accredited representative to participate in the investigation.

So your understanding is correct for international civil aviation, the scope of the Chicago Convention. The US government could delegate a team including experts from the NTSB, the investigation agency, and the manufacturer, perhaps the FAA, the US regulator.
State activities

Will the NTSB be involved in the [investigation]?

Normally the State of occurrence, the State where the accident occurred, has an obligation to contact the States listed in §4.6, and ICAO, and arrange with them their participation (§4.1).
However in this case, the aircraft was operated by Iran Air Force. Per Art. 3 of the Convention), the aircraft is a State aircraft and the convention is not applicable:

a) This Convention shall be applicable only to civil aircraft, and shall not be applicable to state aircraft.
b) Aircraft used in military, customs and police services shall be deemed to be state aircraft.

The Convention being not applicable, no international treaty (international law) compels Iran to investigate this accident, this is a sovereign matter. If an investigation is conducted by Iran, there is no obligation for them to associate foreign entities.
If at any time the Iranian government sees a benefit in working with the manufacturer or a foreign investigation agency, this can be done on a voluntary basis for each party.
Collaboration of Iran under Chicago Convention
Doubts about Iran willingness to follow Chicago Convention must be weighted by what was done when a Boeing 737-800 of Ukraine International Airlines crashed near Sabashahr in 2020. This case was definitely embarrassing for Iran as they were suspected to have shot the aircraft:

Ukraine was involved.
NTSB was involved.
The flight recorders were analyzed by French BEA which is a reference in this field.
ICAO was involved.
States with citizen fatalities were able to follow the investigation.

From the final report of the Iranian investigation board, released 14 months after the accident:

The disassembling of the flight recorders and downloading the data was performed under the control and supervision of the accident investigator-in-charge using the BEA facilities and experts.
The representatives of the U.S. as the State of Design and Manufacture, Ukraine as the State of Registry and Operator, and France as the State providing service and technical advice participated in the process.
The experts of Canada, U.K. and Sweden, as the States having special interest in the accident by virtue of fatalities to their citizens, observed the process to stay informed accordingly.

A representative from the International Civil Aviation Organization (ICAO) participated in this undertaking to observe and facilitate
collaboration among the States involved.

The conclusion of the investigation was the aircraft had been shot down by an Iranian missile:

The air defense’s launching two surface-to-air missiles at the flight PS752, UR-PSR aircraft, the detonation of the first missile warhead in proximity of the aircraft caused damage to the aircraft systems, and the intensification of damage led the aircraft to crash into the ground and explode instantly.

"this can be done on a voluntary basis for each party": A complication is that Iranian sanctions would require a special export license for any company working with them. See e.g. the investigation of TC-TRB where Bombardier noted they were prevented from sharing certain results of their work.


text:
Are there common standards for aviation graphical user interfaces?
I'm searching for graphical user interface in aviation guidelines.
Yet I miss the correct terms and I don't really know where to start.
Let's take an example:

what's the meaning of the green color?
what's the meaning of the pink color?
is the color code regulated?
is this look (color, fonts, layout) regulated globally or does this vary by airplane type?
…

I guess that's a bit of a naive question but I gotta start somewhere.
A bit more Background: I'm a graphic designer. I have to create a web-interface for a national air rescue service. They want the look and feel to be as aviation specific as possible. The web app won't be used in the airplane itself so it is not regulated and it provides non-critical services.
One thing is that the interface should look cool and "techy". But on the other hand I don't want to use colors or layouts which are either very regulated or have a highly specific meaning.

You may look at §5.8 of AC 25-11 which is related to EFIS (also HFDS). In this case, green is for data that are "set", magenta for "targets/goals/objectives". 167 kt is the target speed for the autopilot/autothrust (currently 173 kt). Baro 1700 means the "decision/descent height" has been set by the pilot to 1,700 ft and is measured using the barometric altimeter (not the radar altimeter).

Just to know: How much are you into aviation? Have you ever had something to do with it or are you completely new?

@Pondlife maybe it's better to open a new question on standardization, and leave this one more towards "how can I find out what the values and indicators on the aircraft instruments mean?"

@NoahKrasser I'm a total noob. But as a interface-designer I absolutely love cockpit photographs.

@Thunderstrike Maybe; the OP does ask about both specific details (colors) and general standards so there's certainly an argument there for splitting it. The question is quite broad as it's currently written, which is one reason I edited the title: to try to make it a bit more focused.

@Thunderstrike I think your title edit makes sense. And splitting would also make sense. But since this is an "entry" question, I'd say the nature of it tends to be quite broad.

@Pondlife I think part of the reason I'm being picky is that I think people have a tendency to close new questions as duplicates and link to answers that never quite go into the detail they should :) 'overly' focusing it here as a specific question/situation might to improve the quality and detail in the long run.

I think your best bet might be going through the Instrument Flying Handbook (PDF, 68 MB) by the Federal Aviation Administration. It has plenty of nice graphics, if you're fine with a lot of other irrelevant stuff in the document. There's also the Chapter 8, Instruments, of the FAA Pilot’s Handbook of Aeronautical Knowledge (PDF), which is a bit more compact.

I'm not sure there are any exact specifications how these things have to look. I suspect the minimum requirements are given in the certification specifications, and how they are then presented may be up to the manufacturer.
For instance, in EASA CS-23.2600B:

The  applicant  must  install  flight,  navigation,  surveillance,
and powerplant installation controls  and displays  so  that  a
qualified  flight  crew  can  monitor  and  perform  defined  tasks
associated  with  the intended functions of systems and equipment. The
system and equipment design must   minimise  flight crew errors, which
could result in additional hazards

I'd interpret "minimise  flight crew errors" to not do anything overly ambitious with the instruments that deviate from the norm, i.e. what everybody else is doing.
In EASA CS-23.2610A:

Each aeroplane must display in a conspicuous manner any placard and
instrument marking necessary for operation.

It does happen that this stuff can be different- while the military is generally more flexible, the U-2 reconnaissance aircraft has a speed indicator that goes the opposite direction.

Thanks for those pdf's that's what I was hoping for. I'll dive into it :)

There are no regulations on what color something has to have as far as I know, but of course, a good color usage is a key part of every good and modern avionic.
Maybe you need some terms relevant for you:

EFIS for Electronic Flight Instrument System That's in general the name instruments that are displayed on a screen instead of steam gauges.
PFD for Primary Flight Display This is the thing on the picture you posted in your question (From a Boeing by the way). It has all information regarding the planes position in the room and a bit more.
ND OR MFD for Navigation Display or Multifunctional Display Those displays are usually located next to the PFD and provide the pilots information about the position on a map, a radar and so on.
EICAS/ECAM for Engine indication and crew alerting system/Electronic centralised aircraft monetoring (system) Those screen are, on small planes integrated into the MFD and on big planes in the middle of the cockpit. They provide the captain with information about the engines and the state of the whole plane.

That's just some terms you can research further on. There are usually thousands of pages about those systems available. Of course also a lot on the color codes.

is this look (color, fonts, layout) regulated globally or does this vary by airplane type?

It is actually. There are of course differences but only small. Compare a Boeing PFD and an Airbus PFD. They will look the same at the first look. And also in other EFIS like the Garmin G1000.
Some things about color used in the ECAM (Airbus):

Level 3 Failures: red warnings, situations that require immediate crew action and that place the flight in danger. For example, an engine fire or loss of cabin pressure. They are enunciated with a red master warning light, a warning (red) ECAM message and a continuous repetitive chime or a specific sound or a synthetic voice. The chime can be silenced by pressing the master warning push button.
Level 2 Failures: amber cautions, failures that require crew attention but not immediate action. For example, air bleed failure or fuel fault. They have no direct consequence to flight safety and are shown to the crew through an amber master caution light, a caution (amber) ECAM message and a single chime.
Level 1 Failures: Cautions, failures and faults that lead to a loss of system redundancy, they require monitoring but present no hazard. Examples include the loss of DMC3 when not in use. Level 1 failures are enunciated by a caution (amber) ECAM message only (no aural warning).

Source
Or about the EFIS:

Traditional instruments have long used color, but lack the ability to change a color to indicate some change in condition. The electronic display technology of EFIS has no such restriction and uses color widely. For example, as an aircraft approaches the glide slope, a blue caption can indicate glide slope is armed, and capture might change the color to green. Typical EFIS systems color code the navigation needles to reflect the type of navigation. Green needles indicate ground based navigation, such as VORs, Localizers and ILS systems. Magenta needles indicate GPS navigation.

Source
That means you are free to use any color you want, but of course it's good practice to use the standards. And as graphics designer, I'm sure you know the mean of the different colors.

RED (Often flashing) Warning - Immediate action required
ORANGE/Yellow (Amber often used in aviation) Attention - No immediate action required
GREEN Success
BLUE Information

This is the way normal people in everyday-applications are used to understand color. In avionics, this is similar, however some colors are indeed used consistent across the industry and are reserved for specific events. More below:

Analyzing a PFD (Boeing type)

Source, Added squares
I found this Boeing PFD with like everything displayed that can be displayed on a PFD. This shows the color codes used perfectly. I marked all different elements in a specific color:

MAGENTA The color used for an aim, the aircraft has to reach. For example the speed on top of the speed-strip at the left, the selected altitude at the right or the two bars in the middle, the flight director, which guides the plane how to fly, simplified said.
GREEN Every variable that is set to a specific value, is displayed in green. For example on the left, the numerous numbers at the speed strip, are v-speeds for flaps, gear, rotation and so on. Or also the BARO, which shows the selected QNH.
WHITE Things in white is just information. Like at the bottom right, there is only a reference to the standard QNH or at the bottom center of the artificial horizon you can see the radar altitude (RA).
RED Red is as always the warning color. In this picture this is the two red, dotted lines at the top and bottom of the speed-stripe. They indicate minimum and maximum airspeed. Or the big PULL UP message, saying the pilot he has to pull up the plane because of immediate danger of terrain or an excessive sink-rate.

NOTE: Magenta is also used on navigational displays (maps and CDIs) to indicate a GPS-route, whilst green is used for things like VOR and ILS.

One thing is that the interface should look cool and "techy". But on the other hand I don't want to use colors or layouts which are either very regulated or have a highly specific meaning.

I don't know what your web-interface will be for, how critical the information is and by whom it will be used. However, because you want to let it look like an avionic I assume it will be made for pilots. As you said it's a rescue service, what looks time-critical for me. I would recommend a dark design, as every avionic with bright, saturated, well-chosen colors, to emphasize important parts. Combined with a modern monospace font, it is going to look terrific. (Interface designer is such a cool job :) )

Magenta is also used as a "target" color -- heading bug (target heading), set altitude, desired course line on the map, etc.

So good. Thank you very much for that thorough examination.

@KSPR Would you mind sending a screenshot or two if you are finished? I'm just too curious how it will look like :)

In ECAM and EICAS systems colors have a meaning:

Red - Failure requiring immediate action.
Amber -   Crew awareness; need not take immediate action.
Green - Item operating normally.
White - Titles/remarks to guide flight crew.
Blue - Actions to be carried out, or limitations
Magenta - Messages that apply to a particular piece of equipment/situation (e.g. inhibition messages)

Source: https://www.aviationmatters.co/what-are-eicas-and-ecam-systems-on-aircraft/

Are these standardized/mandated colors by some sort of regulatory body, or are they one manufacturer's color choices, or have they become "standard" through common use? Some explanation on that point would be helpful


text:
How to calculate variable pitch propeller parameters?
I'm carrying out a project on Variable Pitch Propellers for UAVs and especially self-adjusting or Passive Variable Pitch Propellers that change pitch due to aerodynamic forces and Pitching Moments.
At the moment I'm working on a single element (sectional airfoil) using blade element theory for three different stages of the aircraft: Take-off (with a given high RPM,e.g 2000), Cruise (medium RPM,e.g 1000) and landing (low RPM e.g 500) and corresponding free stream velocities 0 , 80, 20 m/s respectively.
However while I'm trying to calculate first Lift and Drag and then Pitching Moments, I realized that there are unknown factors needed for the calculations such as lift and drag coefficients as well as Angle of Attack on that sectional blade element.
The purpose is to use at first a symmetric aerofoil with no camber and I was wondering whether I have to use a commercial aerofoil such as NACA and if so, how to get the Cl and Cd from this aerofoil.
My questions are:

How to calculate the angle of attack or pitch angle while I know their subtraction?
Do I need to give some values for a new parameter that will help to find  these calculations or RPM, Vinf, and r of the propeller is enough?
What about the chord length; do I need to give a random value there?

I am sorry if some of the questions are silly but I'm coming from a different background and I'm fresh in the aerodynamic field.

Related: https://aviation.stackexchange.com/questions/31271/how-to-design-a-propeller-for-uav

How to calculate the angle of attack or pitch angle while I know their subtraction? What does subtraction mean in this context?

Also - in full scale aircraft the propeller speed is often kept constant and only the blade AoA is changed, it takes time to speed it up. Is there a particular design requirement for the large variety in RPM?

By subtraction i meant the angle φ = β-α

There are a couple of key parameters in propeller design, the main ones being the power to drive the propeller, and the thrust that the propeller delivers.

A blade element of a propeller looks like the figure above, from E. Torenbeek, Synthesis Of Subsonic Aircraft Design, which shows the characteristic angles:

The angle between blade chord and propeller plane is the geometric pitch (blade angle $\beta$)
Angle of attack of the blade element $\alpha = \beta - \Phi$
The effective pitch angle is $\Phi = arctan (V / \omega*r)$. This is often given relative to rotational speed $n$ = rounds per second of the propeller, and the propeller diameter R:
$$ \Phi = arctan \frac {V}{n \cdot D } * \frac{1}{\pi \cdot r / R}$$

The advance ratio J of the propeller is
$$ J = \frac {V}{n \cdot D}$$
Induced velocity should be constant over the blade, implying that $\beta$ decreases linearly with increasing r: the propeller blade twist. Because the twist changes linearly, one point on the blade can be taken as the representative blade $\beta$, and this is usually taken at either 70% or 75% of the radial distance.
It can be shown that for a given blade geometry, the power and thrust coefficients $C_P$ and $C_T$ of the propeller are determined only by J and $\beta_{0.75}$. If tip speed is below speed of sound and the blades are not stalled, Mach and Reynolds number effects are negligible.
$$ C_P = \frac {P}{\rho \cdot n^3 \cdot D^5}$$
$$ C_T = \frac {T}{\rho \cdot n^2 \cdot D^4}$$
We can now look up $C_P$ as function of J in for instance NACA reports from the NACA server (check NACA WR 286). Unfortunately these diagrams are not given in metric units, so would need to be converted. But there are many other sources, such as underneath from a question on this forum.

Regarding the profiles: propeller design is pretty specialistic but old fashioned NACA profiles are still being used in helicopter blades for both main rotor and tail rotor. For a symmetrical profile NACA 0012 would be a representative choice, again available from the NASA report server, for instance NACA TN 4357. A google search on NACA 0012 data results in lots of hits. A reference book on this is Theory Of Wing Sections by Abbott & Von Doenhoff.
For the chord length, you may want to have a look at existing propeller designs and their aspect ratio (propeller radius/avg chord). You could start with a value of 15 -20.
There is quite some more info on propeller design for the pre-design phase that you are in, in Torenbeek's book referenced above, including on design for variable incidence props.


text:
What are the main components of the Airbus fly-by-wire system? Is ECAM related to FBW?
I'm assuming that all commercial Airbus planes use a similar, if not identical, system. Can someone give me an overview of the parts of the Airbus fly-by-wire system?
I've also heard of ECAM. Is ECAM related to fly-by-wire?

ECAM and FBW are not directly related, but information and alerts regarding the flight control computers and actuators are displayed on the ECAM screens, like any other information not visible on the primary flight display or the navigation display.

Fly-by-wire
The fly-by-wire concept is actually simple:

In traditional aircraft, the control surfaces like ailerons or elevators are linked to the control inputs used by the pilot, e.g. the column. This link can be direct (cable) and/or amplified (hydraulic or electric actuator commanded by the pilot).

In "FBW" aircraft, the control inputs are instead sent to calculators which deliver actual orders to actuators. Each FWB system, in addition to introducing calculators into the pilot-control surface chains, also gets information from sensors to measure the aircraft response to orders (feedback).

This design has two advantages:

There is an actuator (e.g. an hydraulic jack), so the pilot (or the autopilot) has to exert on the control inputs only a fraction of the actual force that needs to be exerted by the actuators on the control surfaces.
More important for the concept, the calculator can supervise the pilot commands, so that the aircraft is never put in unwanted or dangerous configuration, e.g. stalled. This system is similar to the full authority digital engine control (FADEC) used for the engines.

The main calculators for Airbus A320 family are:

ELAC: elevator and aileron computer
SEC: spoiler and elevator computer
FAC:  flight augmentation computer
SFCC: secondary flight control computer

They are redundant and some functions dedicated to one computer can also be executed on other computers.

Source: Fly By Wire Systems Explained
Actuators are moved using a transfer function from pilot input. In simple words, some correspondence links the actuator deflection to the pilot input. These correspondences are usually named "flight control laws". Airbus uses 3 laws:

Normal: When everything needed by the calculators is available. Maximum protection is available. Sidestick inputs by the pilot are converted into vertical G-load demand and lateral roll rate demand.
Alternate: When some calculators required data are not available. Some protections may be lost and sidestick lateral inputs are converted into a direct equivalence in control surface deflection angle.
Direct: When no protection can be provided by the calculators, due to calculator failure, missing input, actuator or control surface failure. Vertical and lateral sidestick inputs are directly converted into a proportional surface control deflection. Basically the aircraft is a non-FBW aircraft.

ECAM
In parallel instruments in general have evolved from gauges to electronic displays. The elimination of the third crew member (the flight engineer supervising engines, fuel and other parameters) has led to automatic supervision of aircraft parameters and filtering of displayed information.
By default, only a few parameters are shown to the crew, other are replaced by alerts when something is unusual or requires attention. The crew has also the possibility to display parameters/status on demand, e.g. the status of the cabin doors or the fuel tanks. The electronic centralised aircraft monitor (ECAM) is just such system which monitors and displays alerts and important parameters.

A319 ECAM after an actual electrical failure, source
The ECAM system includes two displays that can be configured by the crew:

Source

Relation between FBW and ECAM
Airbus FBW reconfigures laws when one of the flight control computers has failed. Because knowing this reconfiguration is vital for the crew and it follows some failures, this leads to alerts, information and suggestions being displayed on the ECAM screen. However this use of ECAM is not particular to flight control computers.

ECAM indication of autopilot being off, and laws being changed, source
For more technical information about this topic, see question: Is a Control Law Degradation in Airbus Planes displayed on the ECAM?

Thank you, @mins. I appreciate the time you put in your answer. Are the FBW computers, such as the ELAC, embedded systems like microcontrollers? Or do they run specialized Operating Systems?

@MathFlyer: I don't have an answer to that, but you may ask a new question or look at the comments under this answer.

@MathFlyer, each computer is composed of two dissimilar boards. On A320, one uses i386 and one a m68k CPU; I believe they use arm and some newer x86 version new models. Each board runs a different real-time OS (I think one is QNX; can't remeber the other) and each runs independent implementation of the algorithm. One board feeds the output and the other verifies and shuts down the unit if the outputs disagree. Each unit exists in multiple copies that work as fail-overs.

@MathFlyer, note that there is no pressure to miniaturize the boards, so they are similar to normal computer components and made for durability, but in programming style they are microcontrollers—each running a single, relatively simple (couple thousand lines in C) control loop.


text:
Is it possible to get a list of flights at a specific geographic location and specific time?
I would like to know if it is possible to achieve a list of flights that flights above range ring (specific geographic location, range distance), for example the list of flights that passed above London at some date.

Welcome to aviation.SE! This sounds a little bit off-topic/broad for this site, but I will leave the decision to others.

To the compulsive downvoters: try to leave a comment on why the question is not good, and how it could be improved especially if from a newcomer, you are not helping anyone with your behaviour.

No, that is not possible, but check out fr24.com


text:
What happens when you call 866-GA-SECURE in the US?
I live in the US, near a fairly dangerous road, and I've called 911 a few times to report car accidents outside my home.  It's a lot like giving a PIREP - you give the necessary information and the appropriate help is dispatched.  All very simple and clean.
I've never heard of anyone calling 866-GA-SECURE.
What happens when you do?  Who do you talk to?  Who responds?  How fast is the response?  What can you expect?

I don't know, unfortunately, but I love this question. I've always wondered. I think that it's an AOPA number, so likely not much?

@egid: yep, it's an AOPA number: http://www.aopa.org/News-and-Video/All-News/2004/October/6/House-appropriators-fund-AOPA-Airport-Watchs-866-GA-SECURE.aspx

If it isn't worth calling 911 for than there is probably no need. Generally speaking in my experience everybody knows everybody who's anybody at a GA airport, unless they are pilots visiting in which case they normally check in. SO I would say if you talk to someone else on the field they will probably just be like "No that's just Bob" or "Yeah we talked to him already" and if not they will go check it out. At that point they will know right away whether they need to call 911 or not. I think the GA-SECURE thing is mostly to keep the TSA out of small airports because they violate our 4th rights

Although I suppose if you show up at an airport at 2am and nobody else is around and you don't want to call 911 than the 1-866-GA-SECURE might not be a bad option.

It's called the "TSA General Aviation Hotline" on the TSA's website. http://www.tsa.gov/stakeholders/security-directives.  I guess when congress funds it, they call it what they want: (http://goo.gl/ZaBCQA)

@p1l0t might be better to call the local police station or the boss of the FBO... Shorter response time and less hassle.

Yeah if you know the boss's number or there is a afterhours number posted on the door that's probably the best.

OK, I did a little digging and here's what I can definitively tell you:
1-866-GA-SECURE is a joint venture between AOPA's "Airport Watch" program and the TSA.
The hotline is staffed by federal officials and can be used for reporting suspicious or unauthorized activity - e.g. the theft of an aircraft, someone prowling around on the ramp after hours, etc.
The folks answering the hotline will be able to contact local law enforcement (and being that they're federal officers making the call instead of Joe Pilot, they may get a quicker response than you would), but police dispatch isn't their primary function.
The TSA's own guidance on this hotline indicates that it shouldn't be your first resort -- they would prefer that you contact:

Airport management/operations/FBOs
Particularly at fields that are attended 24/7, and those with security or police presence, calling the folks on the field will often give the fastest response, and they should be your first call.
The TSA Hotline (1-866-GA-SECURE)
For fields which are not attended / don't have a security or police presence, this can be an effective way of getting law enforcement to the field quickly.
911 or other local law enforcement emergency numbers
In situations with immediate and potentially dangerous consequences, or ongoing criminal activity (breaking into aircraft, bypassing gate locks, etc.) calling local law enforcement's emergency number / 911 is The Right Thing To Do.

In all cases you can follow up with a call to the TSA hotline to confirm they're aware of the incident.  Whether on an initial call with an ongoing situation or a follow-up the hotline folks will want the basic 911 information (Who you are, Where you are, and What your emergency/situation is). Obviously depending on the situation they may ask for additional details - e.g. if you're reporting that a plane was stolen it would be very helpful if you could provide the registration number.
AOPA's GA Security course covers a bit more of what you may be asked for / about, and the kind of things you should be looking for when informing any of the above authorities of suspicious activity.

Who responds to your hotline call and how quickly they respond is less definitive: It will vary depending on where you are and the local resources available.  A grass strip many miles away from the closest police presence at 3 AM will obviously have a longer response time than a 24x7 attended field with a police presence on the field, no matter who you call.
Typically the first response will be airport personnel (if the field is attended) or local law enforcement (and obviously that will be the case if you're calling the airport's management/operations office or the local police directly).  Whether or not federal authorities get involved in the response would likely depend on what you're reporting.

Awesome! How did you find this all out?

@SteveV. Since the hotline was AOPA's baby (they just got Congress to fund it and staff it) I bugged them :)


text:
What is breaking away/peeling off in military lingo?
About breaking away or peeling off:

Is this synonymous of a wing over?
Is this a signal to your wing mates that you are leaving formation deliberately to engage the enemy?
Does that mean you would subsequently roll on your back to scan for possible enemy aircraft below, complete the roll, and proceed toward the enemy?

I believe these are slang terms for element separation, where a leader and wingman break formation from each other either in order to reform in a new formation for tactical purposes e.g. Spread formation etc. fly a tactical maneuver to defeat a threat like a champagne or in order to land flying an overhead approach.  Wingovers are aerobatic maneuvers, very similar to Lazy Eights, intended to teach student pilots the art of flying the airplane with constantly varying stick and rudder inputs and are not involved with element separation.


text:
What Height Atc radar reads from pilot selection
Just want to know whether ATC radar always reads aircraft height with respect to standard altitude setting or will read the change in height if we select QNH instead of standard 1013 hPa (QNE)?

Wait a second... QNH altitude is based on a "ground" (sea level) pressure of 1013 hPa, no? QFE altitude varies according to air pressure at local ground (with "local ground" always being an altitude of zero, whatever that means in terms of air pressure).

@MichaelKjörling: QNH altitude is based on a "ground" (sea level) pressure of 1013 hPa, no? No, QNH is assumed pressure at sea level (computed from QFE). QNE is 1013.25 hPa as indicated in the question.

The altitude reported by the mode C of the transponder is based on the standard altimeter setting (29.92 in the United States)

sir do you mean that if pilot changes its altimeter setting even then the height send by transponder to radar scope would be that of standard 29.92?

@abbasi: Yes. This makes the reported altitude unambiguous even when the QNH is lower than standard, and eliminates the possibility of separation errors caused by pilots setting the altimeter wrong. The ATC computers can convert the result so it is displayed to controllers with QNH corrections for aircraft below whatever the local transition altitude is.


text:
What are the relations between stability, controllability and maneuverability?
As preparation for my CFI checkride I have been trying to understand aerodynamics very well. One of the things I’m struggling with is stability
If I have a stable aircraft, this means is less controllable and less maneuverable, right?
Do this means an F-16 is poorly stable but very controllable and maneuverable? And a Cessna or a B737 are stable with less controllability and maneuverability?
Thanks for your help guys

Several answers to this question on here, but I don't know how to link them for you.  Basically yes, stability and control are n opposition.

a control system is "stable" if, upon a perturbation (like a gust or up/downdraft), the system will naturally return to its unperturbed state with your hands off the controls.
a plane exhibits "neutral" stability if, upon a control input from the pilot or a gust perturbation, the plane will not right itself if the pilot takes his or her hands off the controls, but neither will it diverge and fly itself into a steeper turn, roll, or pitch attitude hands-off.
"negative" stability means the moment you take your hands off the controls, the plane will by itself pitch up or down, roll left or right, or skid one way or the other. it cannot be flown hands-off unless it has an artificial stability augmentation system built into its control hardware.
A control system is "controllable" if pilot input is successful in recovering from a perturbation. But without pilot inputs, a "controllable" system will not necessarily by itself recover from a perturbation.
Maneuverability refers to the airplane's overall sensitivity to control inputs from the pilot and the effectiveness of the control surfaces over their control range.
An airplane that is highly maneuverable MIGHT be unstable- that is, it MIGHT  not fly hands-off because of how sensitive it is to control inputs or gusts. In general, a high degree of maneuverability usually is associated with marginal stability.

just dropping a comment which might help the OP understand that there are static stabilities and dynamic ones: http://www.boldmethod.com/learn-to-fly/aerodynamics/3-types-of-static-and-dynamic-stability-in-aircraft/

If I have a stable aircraft, this means is less controllable and less maneuverable, right?

Image source
Controllability:  Above depicts a ball in a cup: the centre situation is a statically stable equilibrium, you need to actively deflect the ball from equilibrium and it will want to return to the centre if released. That is how you want the aircraft to be as well, statically stable. When the ball is released it will eventually return to rest in the equilibrium state after some number of overshoots: it is dynamically stable as well. If there was no friction and/or aerodynamic damping, the motion would continue forever: the system would be statically stable and dynamically neutral.
You definitely want a stable aircraft in order to be able to control it, an unstable aircraft is harder to control: the ball wants to roll away all the time, and you need to actively roll it back up the hill. How hard to control, that is a function of the time period of the unstable motion. In helicopters for instance, this is in order of 10 seconds: it is unstable in the hover, but the unstable motion is slow enough for humans to learn how to compensate for it. An F-16 at cruise speed has artificial stability, it is aerodynamically unstable but an active control system provides stabilising inputs without the pilot noticing them. So from the pilot's perspective, the aircraft is stable and relatively easy to control.
Manoeuvrability: Responses to flight control inputs are indeed a function of how aerodynamically stable the aeroplane is, but also of the control volume: surface area times distance from Centre of Gravity. Install a big enough elevator and a stable aeroplane will make lovely loopings. Aerobatic aircraft are aerodynamically stable and very manoeuvrable.

This might help
Stability - Imagine a stick hold it at the top and then displace it. It swings and then hangs straight. This is a dynamically stable system. Now take the same stick and stand it on your hand, this is a dynamically unstable system and you have to make constant corrections to keep it standing. (aeroplanes - Dynamically stable / Helicopters - Dynamically unstable)
Control-ability - Capability of an aircraft to respond to the pilots control inputs. If an aircraft fails to respond to a pilots inputs (or responds n the opposite manner), then it lacks control-ability. Some examples are high speed control reversal, mach tuck, control lag through inertia, and control authority to dampen oscillations eg Dutch roll or spiral dive. The ability to recover from a spin (A/B ratio) or a stall.
Manourverability - the ability for the aircraft to commence and sustain maneuvers, its responsiveness (eg control effectiveness) and its performance eg rate of roll, or turn and pitch rates(G load)


text:
Is it conceivable that carburettor icing alone could have caused the power loss?
A few days ago, one of our Club's planes, a Robin HR200, had to make an emergency landing shortly after T/O. It reached about 410ft AGL when it suddenly lost power, the FI took control from the P/UT and put it down in a field. The crew is fine, and the plane undamaged.
The current explanation of the CAMO is Carb Ice, which I'm struggling with. It'd be great to get some feedback from the hive mind as to what possible causes we should maybe continue to investigate.
Thus, the question is:
Is it conceivable that carburettor icing alone could have caused the incident?
The events and possibly relevant detail in order:
The plane was filled up in the morning and flew 89 minutes, with a stop at a different airfield, without issue. The P/UT had recently passed his first progresscheck and was supposed to begin pattern training. He had done a thorough preflight incl draining etc; which was overseen and double-checked by the FI.
Generally, the plane is maintained in a CAMO contract and was in service for just over 40 hours after its last 50hr check.
The engine was normal, although the FI reported that it took a second or two longer than normal (about 7 seconds), but that may have been due to the P/UT priming the engine differently. Presently I don't believe this is relevant.
All checklist items were completed and double-checked. Taxi with just the engine fuel pump was normal (the boost pump is off during taxi, but on for engine start and T/O).
The runup checklist for the HR200 is split into 2 parts. The first one contains set parking brake, T&P checks, Mixture rich, Mag check, Carb heat check etc. The second one safety items (seats, belts etc), trim settings, fuel pump on, flaps as required, lights, transponder etc.
In between those two, the crew briefed emergency procedures during T/O roll or initial climb which is standard in our club. This may have taken up to 2 minutes due to the experience of P/UT - this may be relevant as on line up the carb heat check would be around 2.5 min in the past, with the engine at around 1000 RPM since then.
The takeoff roll was normal. The student remembers double-checking the Throttle to be fully in, the FI remembers checking engine indications with everything being green. The FI can't remember the exact RPM but that the power and noise "felt" was normal, as was the rotation point.
Due to the wind, the FI requested the student to accelerate slightly beyond Vy to about 70 kn shortly after T/O which he did. Upon reaching the max Alt of 410 ft AGL, the engine suddenly lost power but kept running. The FI took control and changed the attitude to best glide. Carb heat was set before even checking Mixture, and was kept warm until touchdown. Mixture, primer, ignition etc were checked. There was no time to use a checklist but the FI had about 3200 hours, and several hundred on type, so I believe that everything sensible was done.
W/B was close to max (761 kg); CG about in the middle of the normal category at ~0.38.
WX was between these two metars, so RH about 80-85% at OAT of 8 Celsius.
1250Z 23011KT 9999 FEW020 08/04 Q1013
1420Z 24011KT 9999 -DZ SCT019 08/05 Q1014
After emergency responders left the scene, an engine test was performed about 3 hours after touchdown. The engine started, but ran very rough. The mixture was leaned out, and several seconds after that the engine appeared to "breathe" and began to run normally.
(I'm awaiting a more detailed recollection of how this test played out and will update the question - ie how long it took to start etc)
The next day, an engine inspection was performed. Spark plugs were replaced; the lower ones had some lead on them (which is reasonably normal with the O-235, generally they indicated a slightly rich mixture from the previous runs.
Now I need to positively exclude any possibility other than carb icing, which is my struggle with the explanation. I cannot let return a plane to service (one of our main trainers), if there is a chance for a different, latent problem.
It's thinkable that the throttle valve accreted some ice in the runup area, but only to the extent that the difference in power after full throttle would not be evident to a highly experienced FI, and the ground run according to the PowerFlarm readout was normal (although it only records every 4 seconds, so it's not super accurate).
If there was icing initially, it's further thinkable that further ice accreted to the existing one with the throttle fully open. However, in that case I would have expected a gradual, not sudden, decrease of power, at least over a period of a few seconds. The plane did not fly through any visible moisture, so icing of the air filter can be excluded. Also, using carb heat would have immediately rectified such a problem.
How can I reconcile icing with the sudden loss of power around 40-45 seconds into the flight? Carb heat was turned on almost immediately, and kept on until touchdown approximately 1 min and 5-10 seconds later.
Initially, my first thought was a vacuum lock in the tank or downstream, with a reduced airflow to the tanks. That would be consistent with the FI's feeling of the engine running better with reduced power, she was smoothly alternating the power lever from full to idle and back. The accelerator pump, when putting power back in, appeared to give a short boost of power albeit for a very short time before returning to rough running.
Please comment additional questions for me to investigate below; I shall try to reply and update this post with answers or additional clarification where required.

The site is not supposed to be used to collect opinions, it works on a closed question / factual answer model. What is your question?

The question is whether Carb icing could be the sole cause of the incident. I'll try to rephrase my question accordingly. Thank you for the comment

Speculation on the causes of accidents that are still under investigation are specifically off-topic here. See [help/on-topic]. FWIW, loss of power at 400ft AGL is a serious problem that has to be dealt with immediately, whatever the cause. The instructor did exactly the right thing and the aircraft and crew are safe. For the rest, we wait for the official report.

It wasn't an accident, it was an incident @CatchAsCatchCan, and there's isn't an official investigation.

I also feel like we can't give anything but opinion here, and so there's no "right" answer. I'll refrain from voting to close, but if I was a normal user I probably would.

Unfortunately speculation is all I have left; the authorities will not investigate. I am the accountable manager for our A/C. If someone could point me towards a more suitable forum with the same level of experience I'd appreciate it, and would then even support a vote to close

This was a case of carburettor icing. Conditions were in the regime of high probability of carburettor icing in any power setting. All aviators should know this!

@Jpe61 I'm glad you are so sure. At full power, with a normal takeoff run an initial climb, followed by a sudden power loss of (calculated) 1400+ RPM. I shall be interested to learn what you think exactly happened technically there with the ice. That's the kind of explanation that I'd be after. Of course every aviator knows what carb icing is, your comment comes across slightly offensive.

Would you agree with my comment though? As per the question carb heat was not on during t/o. This is clearly a mistake, since OAT of 8°C and dewpoint of 4 is very much a heavy carb icing condition, and not vapor lock condition at all. Water in fuel was checked twice, none found. No anomalies detected in engine inspection. Use occam's razor.

@Jpe61 Unfortunately I cannot. Having Carb heat on with full power is more likely to generate detonation inside the cylinders than prevent icing.  You are right with regards to the conditions, which I happily agree to - on any lower than full power carb heat must be applied.
A locked valve or reduced pressure relief to the fuel tank is high on my list of suspects to check, too. Carb heat I find hard to align with what happened.

@ExternalUse but icing could have caused an excessive lean setting, causing engine failure at 400 feet from overheating, or from excessively rich.  Is there any data on cylinder head temps?  Did the engine have enough oil?  How long was carbon heat ON during runup?

@RobertDiGiovanni Oil was sufficient; T's & P's were green. No CHT data (very simple trainer A/C). But, as of yesterday icing is prettys much off the table - it ran fine in the lower RPM regions but reasonably rough with some misfires in the higher power regions. Unless the mechanic who checked it over, replaced the spark plugs etc introduced something new (ie forgot a cable or sth - it's field surgery after all) then I believe the report of the initial run on the evening of that landing to be wrong or incomplete, there's definitely sth off. I'll write a comment here once I know the result.

As phrased, this question is answerable but hardly helpful... is it conceivable that carb icing...?  Sure, it's conceivable. All sorts of things are conceivable. Doesn't mean that they're likely, or that one of them is what actually happened. Maybe a more discussion-oriented board like PPRune would have a forum where this could be kicked around at greater length, but as it stands, this question & its comments have exactly the sort of speculations that show why it's a terrible fit for this site, and will remain closed.

@RalphJ please see the comment thread below the answer; I've already accepted that. But thanks for the suggestion on the forum, that's actually helpful.

You are right to question the carb heat explanation, I'm not buying that either given your detailed timeline. Carb heat can definitely cause an engine failure, but usually there's going to be a power loss first. Also, given carb heat had been on as part of the run-up checks a few minutes before its unlikely enough ice had a chance to accumulate.
After an engine failure due to carb icing the residual heat from the engine will almost always melt the remaining carb ice, and the engine sparks to life immediately. You say the engine ran rough at first, which is more consistent with a case of fuel contamination. So, that's is a more likely explanation than icing.
Whichever the case, I'd be on the instructors like a rash, as it seems possible someone was lax about carb heat or draining the tanks. Even if that isn't the explanation it does not hurt to use this incident as a reminder to be diligent.

In the absence of a full investigation, which is not going to happen, we have to look at likelihoods and see what improvements could be made for safety. The stated reason of carb icing is less likely than another explanation which fits the information in the question. While I accept that I cannot give a definitive answer of what exactly caused the failure, I can certainly suggest actions which will improve safety down the line.

Thanks @GdD, I've discussed a few improvements with our HT already. Here for example, the crew didn't observe the RPM before and after applying Carb heat during the runup; something I learned differently for example (I still call out "no rise, no ice" to myself). Carb ice certainly is a possibility, and likely a contributing factor. It's just sad (but accepted, of course) that they can't be discussed in a forum full of intelligent people from the industry.

@ExternalUse I understand your frustration, but Stack Exchange is not a forum, and in your case, the strict policies regarding questions are against you.

Understood, and accepted.